Thread cutting device for buttonhole and similar sewing machines



April 20, 1937. H. PUDELKO 2,077,531

THREAD CUTTING DEVICE FOR BUTTONHOLE AND SIMILAR SEWING MACHINES Filed Sept. 24, 1934 2 Sheets-Sheet 1 H. PUDELKO 2,077,531

THREAD CUTTING DEVICE FOR BUTTONHOLE AND SIMILAR SEWING MACHINES April 20, 1937.

Filed Sept. 24, 1934 I 2 Sheets-Sheet 2 v a Z 7 M z m 2 2 "w 1 7 1 7 r@ 2 a A a M f v a 7 I! mwm u f x a: m

Patented Apr. 20, 1937 UNITED STATES PATENT OFFICE THREAD CUTTING DEVICE FOR BUTTON- HOLE AND SIMILAR SEWING MACHINES Hermann Pudelko, Bielefeld, Germany, assignor to Diirkoppwerke Aktiengesellschaft, Bielefeld,

Germany 6 Claims.

This invention relates to the arrangement of a thread cutting device on a buttonhole or similar sewing machine for clamping and severing the thread after the last stitch. The known cutting devices of this type are rigidly mounted on the sewing machine and consequently cannot be easily removed, and the cooperation of their members is relatively complicated.

Contrary hereto the device according to the invention is removable and automatically returns into its inoperative position after the severing of the thread or after the first stitch on a fresh button hole. The device is of a novel construction in that it is pivotally suspended at one end and freely supported on an inclined guide at its other end. It consists of two plates shiftable mutually and relatively to a stationary base plate, one of the plates carrying the stationary cutting members and the other actuating the cutting member which swings between the stationary cutting members.

An embodiment of the invention is illustrated by way of example in the accompanying drawings, in which:-

Fig. 1 shows in elevation the arrangement of the cutting device on a sewing machine.

Fig. 2 is a top plan View of Fig. 1.

Fig. 3 shows the cutting device in side elevation, removed from the machine and in inopera- 30 tive position.

Fig. 4 is a top plan view of Fig. 3.

Figs. 5, 6 and. 7 Show in top plan view three positions of the cutting members during their operation.

35 Fig. 8 is a front elevation showing the cutting members in open position.

Fig. 9 is a front elevation showing the cutting members in closed position.

Fig. 10 shows the intersliding of the cutting 40 members.

The cutting device, that is its base plate I, is removably mounted on a bracket 5 by means of a strap 2 suspended between pointed screws 3 and 4, the front end of the device resting 45 on an inclined guide 6. The device is actuated by pedal or the like acting upon a chain I. By exerting a pull on the chain I an arm II will be swung in the direction of the arrow X (Fig. 2) by means of levers 8, I0, so that a roller I2 50 presses forward a plate I3 slid-able on the base plate I. The plate I3 slides at an incline on the base plate I because the plate I3 is guided along slots l6 and I! by pins I4 and I5. A plate I8 slidable on the plate I3 is shifted at the 55 same time until its nose I9 comes into contact with an abutment 26 on the base plate I(Fig. 5) whereupon the plate I3 continues its forward movement alone. The strap 2I fixed on the plate I3 moves forward with this plate.

The plate I8 which has remained stationary 5 after its nose I9 has come into contact with the abutment 20, carries at its front end a strap 22 in which an axle 23 is mounted which now likewise remains stationary relatively to the plate I3. During the continued forward movement of 10 the strap 2!, on which the cutting member 24 is pivotally mounted at 25, this cutting. member 24 will rotate about the axle 23 which is now stationary, So that its cutting edge 26 approaches the clamping edge 21 and the cutting edge 21 15 of the stationary two-part cutting member 28, 28. When the cutting edge 26 has swung completely between the clamping edge 2'! and the cutting edge 21, the thread is clamped on the upper edge of the inclined surface 29 of the cutting edge 26 and severed by the lower edge of this surface 29.

The plate I8 is guided by means of pins 32 and 33 engaging in slots 30 and 3I, in a similar manner to that in which the plate I3 is guided along the base plate I by the pins I4 and I5 engaging the slots I6 and IT. The strap 2| is adjustable on the plate l3, so that the cutting members can be mutually adjusted. The spring 31 serves for gently pressing together the plates I3 and I8.

During the forward sliding of the plate I3 the upper arm of the U-shaped strap 22, which in its inoperative position bears against the inclined guide 6 (Fig. 1), slides downwards along 35 this guide, whereas the base plate I swings downwards about the points 3, 4, so that the cutting members jointly perform an inclined downward movement towards the front and in this manner are brought into the cutting position illustrated in dot-dash lines in Fig. 2.

After the cutting operation the cutting members are pushed back by a spring 34 on the base plate I until they arrive in the position illustrated in Fig. 6. In this position a pawl 36 acted upon by a spring 35 locks the plate l3. During this return movement the cutting edges of the cutting device remain closed and clamp and hold the severed thread until it has been sewn by a few stitches on a fresh button hole, that is until the nose 38 of a lever 40 engaging a presser foot 39 swings the pawl 36 out of its notch 4I, whereupon the cutting device swings completely back into its inoperative position (Fig. 4) under the action of the spring 34. The pawl 36 is disengaged rapidly because the presser foot 39 begins to move forward directly at the commencement of a fresh button hole.

I claim:

5 1. A thread cutting device on button hole and similar sewing machines, comprising in combination a cutting aggregate including besides a fixed and a pivoted cutting member and a clamping member two relatively shiftable plates oscillatably and removably suspended at one end, and a guide s'lidably supporting the other end of said plates.

2. A thread cutting device on buttonhole and similar sewing machines, comprising in combination a bracket on the machine, a strap in said bracket, a pair of adjustable pointed screws as holding means removably and pivotally holding said strap in said bracket, a base plate suspended at one end on said strap, an inclined guide supporting the other end of said base plate, cutting members carried by said base plate, and

means for oscillating said plate in said bracket to impart an inclined downward movement to said cutting members.

3. A thread cutting device on button hole and similar sewing machines, comprising in combination a bracket on the machine, a strap on said bracket, a base plate pivotally suspended at one 7 end of said bracket, two relatively shiftable plates slidable on said base plate, two plate straps one carried by each of said plates, a pin carried by one of said plate straps, a cutting member pivotally mounted on said pin, a fixed cutting member under said pivoted cutting member, a clamping member above said pivoted cutting member, an arm on said pivoted cutting member pivotally connected to the other plate strap, and means for relatively shifting said plates to swing said pivoted cutting member between said fixed cut- 40 ting member and said clamping member to sever the thread.

4. A thread cutting device on button hole and similar sewing machines, comprising in combination a bracket on the machine, a strap on said .5 bracket, a base plate pivotally suspended at one end of said bracket, two relatively shiftable plates slidable on said base plate, two plate straps one carried by each of said plates, a pin carried by one of said plate straps, a cutting member pivot- 5 ally mounted on said pin, a fixed cutting member under said pivoted cutting member, a clamping member above said pivoted cutting member, an arm on said pivoted cutting member pivotally connected to the other plate strap, and means 55 for jointly shifting said plates on said base plate, a nose on one of said plates, and an abutment on said base plate adapted to contact with said nose and arrest the movement of the plate provided with the nose to relatively displace said 60 plates and swing said pivoted cutting member between said fixed cutting member and said clamping member to sever the thread.

5. A thread cutting device on button hole and similar sewing machines, comprising in combination a bracket on the machine, a strap on said bracket, a base plate pivotally suspended at one end of said bracket, two relatively shiftable plates slidable on said base plate, two plate straps one carried by each of said plates, a pin carried by one of said plate straps, a cutting member pivotally mounted on said pin, a fixed cutting member under said pivoted cutting member, a clamping member above said pivoted cutting member, an arm on said pivoted cutting member pivotally connected to the other plate strap, and means for jointly shifting said plates on said base plate, a nose on one of said plates, and an abutment on said base plate adapted to contact with said nose and arrest the movement of the plate provided with the nose to relatively displace said plates and swing said pivoted cutting member between said fixed cutting member and said clamping member to sever the thread, said clamping member having a clamping edge adapted to cooperate with said pivoted cutting member to clamp the severed thread.

6. A thread cutting device on button hole and similar sewing machines, comprising in combination a bracket on the machine, a strap on said bracket, a base plate pivotally suspended at one end of said bracket, two relatively shiftable plates slidable on said base plate, one of said plates having a notch, two plate straps one carried by each of said plates, a pin carried by one of said plate straps, a cutting member pivotally mounted on said pin, a fixed cutting member under said pivoted cutting member, a clamping member above said pivoted cutting member, an arm on said pivoted cutting member pivotally connected to the other plate strap, and means for jointly shifting said plates on said base plate, a nose on one of said plates, and an abutment on said base plate adapted to contact with said nose and arrest the movement of the plate provided with the nose to relatively displace said plates and swing said pivoted cutting member between said fixed cutting member and said clamping member to sever the thread, a pawl on said base plate adapted to engage said notch in one of the shiftable plates to lock said pivoted cutting member in closed position between said fixed cutting member and said clamping member, a spring adapted to jointly return said plates into their initial position, and means for disengaging said pawl from said notch to allow the relative shifting of said plates to swing said pivoted cutting member into its open position from between said fixed cutting member and said clamping member.

HERMANN PUDELKO. 

